netdev - Re: [PATCH net-next v3 1/8] ethtool: Add support for configuring frame preemption

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Message-ID: <874khpns4f.fsf@vcostago-mobl2.amr.corp.intel.com>
Date:   Fri, 05 Mar 2021 14:38:24 -0800
From:   Vinicius Costa Gomes <vinicius.gomes@...el.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, kuba@...nel.org, vladimir.oltean@....com,
        Jose.Abreu@...opsys.com, po.liu@....com,
        intel-wired-lan@...ts.osuosl.org, anthony.l.nguyen@...el.com,
        mkubecek@...e.cz
Subject: Re: [PATCH net-next v3 1/8] ethtool: Add support for configuring
 frame preemption

Vladimir Oltean <olteanv@...il.com> writes:

> On Tue, Mar 02, 2021 at 04:40:55PM -0800, Vinicius Costa Gomes wrote:
>> Hi Vladimir,
>>
>> Vladimir Oltean <olteanv@...il.com> writes:
>>
>> > Hi Vinicius,
>> >
>> > On Fri, Jan 22, 2021 at 02:44:46PM -0800, Vinicius Costa Gomes wrote:
>> >> Frame preemption (described in IEEE 802.3br-2016) defines the concept
>> >> of preemptible and express queues. It allows traffic from express
>> >> queues to "interrupt" traffic from preemptible queues, which are
>> >> "resumed" after the express traffic has finished transmitting.
>> >>
>> >> Frame preemption can only be used when both the local device and the
>> >> link partner support it.
>> >>
>> >> Only parameters for enabling/disabling frame preemption and
>> >> configuring the minimum fragment size are included here. Expressing
>> >> which queues are marked as preemptible is left to mqprio/taprio, as
>> >> having that information there should be easier on the user.
>> >>
>> >> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
>> >> ---
>> >
>> > I just noticed that the aMACMergeStatusVerify variable is not exposed in
>> > the PREEMPT_GET command, which would allow the user to inspect the state
>> > of the MAC merge sublayer verification state machine. Also, a way in the
>> > PREEMPT_SET command to set the disableVerify variable would be nice.
>> >
>>
>> The hardware I have won't have support for this.
>
> What exactly is not supported, FP verification or the disabling of it?
> Does your hardware at least respond to verification frames?
>

Not supported in the sense that the NIC doesn't expose those variables
into registers.

About the behavior, I am asking our hardware folks.


Cheers,
-- 
Vinicius